I used to work with a trainer and I was about 305 when I started with them. They didn't want me running either but it was only because I didn't even have the endurance to walk far. so they had me work up my walking but then had me start jogging. I lost that endurance when I started gaining weight again, but I plan on starting jogging again soon. I say if you have the ability to walk comfortably than give it a try. good luck to you.